CPU, MB and number of PCI Lanes

[rhythm44]

I'm upgrading my PC and am getting confused over what I need in a MB and CPU. Specifically, how many lanes does my PC need to support for my parts to work properly. I'm new to this so these questions may be basic.

 

Here's what I want to install:

2x GTX970 in SLI (8x-8x I assume?)

1x sound card (1x PCIe)

1x wifi card (1x PCIe)

 

Does this mean I need a MB that supports a minimum of 18 PCI lanes? I read somewhere that a MB with 16 lanes will disable the second GPU in SLI when a third PCIe device is installed as this exceeds the lane limit of the MB? Is this correct and how do I tell how many lanes a MB supports?

 

I was thinking about purchasing the ASUS Maximus VII Hero and an Intel 4690k. Does this work?

[Sam Z Man]

The chipset will handle the 1X lanes so your good.

 

The Maximus VII is overpriced though.

[rhythm44]

The chipset will handle the 1X lanes so your good.

 

The Maximus VII is overpriced though.

 

Thanks for the response. Sorry - do you mean the CPU will handle the GPU SLI and the MB chipset will take care of the wifi and sound card?

[-rascal-]

Thanks for the response. Sorry - do you mean the CPU will handle the GPU SLI and the MB chipset will take care of the wifi and sound card?

 

The LGA 1150 CPU's (i.e. i5-4690K and i7-4790K) provide 16 PCI-E 3.0 lanes. They are dedicated to the PCI-E X16 and/or PCI-E X8 slots.

The PCI-E X1 slots on the motherboard are PCI-E 3.0 and provided by the chipset (i.e. Z97).

The PCI-E X1 slots do not share PCI-E lanes with the 16 PCI-E 3.0 lanes from the CPU.

 

 

For most Z97-based motherboards, when you use one graphics card, it is recommended to use the top PCI-E X16 slot. This way, the lanes are disrupted as x16 + x0, when the second PCi-E X16/X8 lane is unused.

 

When you install a second graphics card, the 16 lanes is broken down to x8 + x8. NVidia SLi requires  the PCI-E slots to run with at least x8 for SLi to be allowed / enabled in the drivers.

 

If you were to get say... a budget H97 or B85 motherboard, the PCI-E slots may run at x16 + x4. In this case, even though the system detects two graphics cards, it won't allow you to enable SLi. This is a soft limitation programmed into the drivers; set my NVidia.

 

PCI-E x8 is plenty of bandwidth for graphics cards even like the GTX 980 Ti or GTX Titan X. Running your GTX 970's at x8 + x8 will not be a problem, and you will not see any performance loss compared to running them at x16.

 

The slots are physically X16 in side, but they m ay be electrically wired to run at x8.

Red slot on the right-hand side of the picture is wired for x16.

Red slot on the left is wired for x4.

In this situation, the motherboard (AsRock Fatal1ty H97 Performance) does not support SLi.